If I remember correctly, over the next several decades, we expect the GDP to be negatively impacted to the tune of about 5% or 6%, although it's difficult to be absolutely certain that this will, indeed, be the impact because we're projecting economic growth and the impact of climate change several decades into the future. However, based on what is known about the science of climate change and the overall weather patterns, that's our best estimate.
The numbers you quoted from the Climate Institute I cannot speak to because I haven't seen the analysis, but they seem to be, roughly speaking, in the ballpark and not out of whack to me.